Scroll fluid compressors include fluid compression devices which were designed based on a conceptual technology that was described in 1905 in U.S. Pat. No. 801,182. According to this document, a scroll fluid compressor includes two similar structures named whorls, each of which being a circular plate with a perpendicular wall that has a fundamentally spiral outline. These whorls are inversely coupled together so that the top of the perpendicular wall of the first whorl is in contact with the base of the second whorl, forming a reciprocal coupling. Moreover, in addition to be connected to the other whorl, one of the whorls is attached to an electric motor. The whorl attached to the electric motor is called the orbiting whorl and the other whorl is called the fixed whorl.
According to U.S. Pat. No. 801,182, an element is provided which is capable of providing the orbiting whorl with an orbital movement from the rotational movement of the shaft of the electric motor. The orbital movement of the orbiting whorl, in relation to the fixed whorl, results in a continuous and gradual movement of the points of contact between the orbiting whorl and the fixed whorl. This continuous and gradual alteration between these points of contact produces continuously decreasing chambers. Because these virtual chambers can be filled with various fluids, by feeding the fluids into the chambers, one can compress the fluids.
Generally, the whorls and the electric motor are placed in the same housing (normally a hermetic housing), and, therefore, it is common to secure one whorl against the other whorl through a rigid structure, which is known as a block frame. Accordingly, a conventional scroll fluid compressor has multiple contact interfaces between the moving parts and the fixed parts. Among these contact interfaces, the following are noted: the contact interface between the shaft of the motor and the piping of the block frame, the contact interface between the tops and bases of the orbiting and fixed whorls, and the contact interface between the lower surface of the orbiting whorl and the upper surface of the block frame. Generally, these contact interfaces include “chambers” of lubricating fluids in between the contact interfaces to reduce the contact, and consequently, the friction between the elements.
In fluid compressors, especially scroll fluid compressors, it is common to store the lubricating fluid responsible for lubrication of all the contact interfaces in the interior of the hermetic housing of the compressor. The lubricating fluid is delivered to these contact interfaces by the shaft of the electric motor when the compressor is started up. Subsequently, the lubricating fluid returns back to the “bottom” of the hermetic housing (due to the force of gravity). In this regard, when the compressor starts up, the lower bearings are lubricated before the upper bearings. Thus, after startup of the compressor (i.e., after a few seconds), some of the contact interfaces that use the lubricating fluid enter into direct contact before being lubricated. These contact interfaces tend to be more worn out than other contact interfaces which are lubricated just after the compressor's startup. For example, it is noted that the contact interface between the lower surface of the orbiting whorl and the upper surface of the block frame tend to wear out quicker than the contact interface between the shaft of the motor and the piping of the block frame. This is because when the compressor starts up, the latter receives lubricating fluid before the former.
Delayed lubrication of parts is a significant problem in compressors and can disproportionately affect the useful lives of different parts in a compressor. For example, a compressor can be replaced (or submitted for repair) when some of its parts are still fully functional. Alternatively, the same compressor could be continually used when some of its parts are damaged.
Some have attempted to address these problems. For example, U.S. Pat. No. 7,329,109 describes a scroll fluid compressor in which the contact interface between the tops and bases of the orbiting and fixed whorls include at least one retention recess (to store oil). The retention recess is constructed in a manner to preserve a quantity of oil capable of providing lubrication between these components when the compressor is started up. Moreover, this retention recess, or “chamber,” acts as a seal between the whorls.
As another example, Japanese Pat. App. No. 2002213374 describes a scroll fluid compressor in which the upper surface of the whorl provides a plurality of concavities that optimize the lubrication of the contact interface between the tops and bases of the orbiting and fixed whorls. Perceptibly, the objectives of this embodiment are similar to the objectives of the embodiment described in U.S. Pat. No. 7,329,109.
As another example, U.S. Pat. No. 6,537,045 describes a scroll fluid compressor in which the contact interface between the lower surface of the orbiting whorl and the upper surface of the block frame provides multiple recesses of micrometric depth (from 30 μm to 150 μm). These recesses are specially designed for lubrication optimization of the aforesaid contact interface. These recesses intend to act as pre-reservoirs of lubricating fluid and are supposedly capable of preserving a quantity of lubricating fluid sufficient for lubrication of the components when the compressor is started up.
In any event, the recesses described in U.S. Pat. No. 6,537,045 are too deep. These depths do not allow for creation of a field of pressure that is necessary to provide support for the load. This is because in a film of oil with the special viscosity for the scroll type compressors (ISO 10 to ISO 68), the “height” of the film of oil (in a hydrodynamic setting) is fundamentally defined by the maximum depth of the recesses. When this depth is excessive, the “height” of the film of oil produces a fundamentally null “support pressure,” as described by the classic theory of lubrication.
U.S. Pat. No. 7,422,423 describes an alternative compressor used in refrigeration systems. This compressor provides for a plurality of “contact sections” between the moving parts. In particular, the “contact sections” are spherical shaped recesses, which are configured to cause a vortex flow of the oil retained therein. It is also noted that the aforementioned spherical recesses are shaped through grinding by a machine. Furthermore, the teaching described in U.S. Pat. No. 7,422,423 is especially efficient in lubrication of components making rotational or alternating movement. However, these embodiments do not apply to lubrication of components making orbital movement.